This invention relates in general to wireless communication systems, and more particularly to determining repeater priority in a multi-channel wireless communication system.
Wireless communication systems often support repeaters distributed throughout a geographic area. Oftentimes, the geographic area is divided into coverage areas, each of which is serviced by at least one repeater in the coverage area. In certain mobile communication systems, for example, a mobile unit acts as a repeater between a portable unit in the coverage area and a remotely located base station. The mobile unit, typically based on a vehicular power source, includes a much more powerful transmitter than a portable unit that typically comprises a handheld battery operated radio. In this way, the portable unit is able to utilize the more powerful mobile unit in the coverage area to repeat communications between the portable unit and a remotely located base station.
Additionally, the wireless communication system may include multiple communication channels. A mobile repeater unit operating within the wireless communication system may move from one coverage area to another. If two or more mobile repeater units operate in a single coverage area there may opportunities for a portable unit to attempt to communicate with two mobile repeater units at the same time. Two mobile repeater units transmitting at the same time would cause interference and lost communication. To try to avoid such conflicts in communications by mobile repeater units a wireless communication system may use a priority scheme where only one mobile repeater unit in any coverage area is designated as the priority unit, while other mobile repeater units in the coverage area are designated as non-priority units. A priority unit repeating a transmission between a portable and a remote base station would be monitored by any other mobile repeater units in the coverage area and these other units would remain in a non-priority mode. In this way, normally only the one priority mobile repeater unit in a coverage area would handle repeating transmissions between a portable unit in the coverage area and a remote base station. It is essential therefore that only one mobile repeater unit were in priority mode at any one time so that two mobile repeater units will not attempt to repeat a portable-to-base or a base-to-portable transmission.
This problem is more likely to occur in communication systems where mobile repeater units communicate over multiple communication channels. Each mobile repeater unit, in such a system, typically scans channels searching for a transmission on one of its programmed frequencies. For example, if while a first mobile repeater unit is in priority mode and a second non-priority mobile repeater unit scans channels and detects a transmitted signal from a remote base station unit, for example, with no other mobile repeater unit repeating the transmission to the portable, the second mobile repeater unit may likely count itself into priority mode and begin to handle the transmission. This condition, unfortunately, would put two mobile repeater units in priority mode. During a subsequent portable-to-base transmission, for example, both priority mobile repeater units would attempt to transmit on top of each other thereby likely causing interference and lost communication.
Thus, there is a need for an improved method in a wireless communication system for multiple repeater units in a coverage area to determine priority for a single repeater unit thereby ensuring successful communication is maintained in the coverage area.